310 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of technique were used in the preparations, stained sections, smears aud 

 aceto-carmine mounts. The last two gave the best results. Much 

 difficulty was experienced owing to the stickiness of the chromosomes, 

 and their separation was best found in smears and in aceto-carmine pre- 

 parations, no matter in what they were fixed. Fixation for sections was 

 mostly done in Gilson's, Flemmings or Hermann's solution : the first gave 

 best results. Pieces left indefinitely in aceto-carmine gave very good 

 results, and this led to experiments with other acids (butyric, formic), but 

 neither was as good as acetic. Smears also were made after Guyer's 

 method ; these were fixed in Bouin's solution and stained with iron- 

 hamiatoxyliu. These smear preparations were found to be favourable 

 for drawing and photography and much better than sections stained in 

 the same way. The chief object of the paper was to show that there is 

 no valid evidence that any element which may be justly interpreted as 

 an .^-chromosome exists in the chicken. 



Preparing Teleost Embryos for Class Use.* — Some of the most 

 important features of development of the Teleost egg, such as discoidal 

 cleavage and the part played by the germ ring in the formation of the 

 embryo, require for their satisfactory demonstration that the entire egg- 

 shall be preserved and studied as nearly as possible in the natural form. 

 For this purpose balsam mounts are of little value, for even with the 

 vitelline membrane removed the egg usually collapses in the higher 

 alcohols or in xylol. 



For the convenient handling of cleavage stages to be studied as 

 opaque objects, B. G. Smith has devised the following method. 

 Pieces of | in. glass tubing are sealed at one end by holding in a flame ; 

 a few eggs fixed in corrosive-acetic and preserved in formalin are placed 

 in each tube and the opening plugged with cotton. For these stages 

 it is well to choose an egg with dark yellow yolk, this will aid in the 

 differentiation of the snowy white blasto-disk. The eggs may be studied 

 by dropping the tube into a watch-glass filled with water and examining 

 them with a lens ; or the tube may be held in the hand and examined 

 with the lens. The special advantage of the tube is that of ease of 

 manipulation : any view desired can be secured and that without injury to 

 the egg. An additional advantage is that the method allows little trouble 

 from the inevitable mixing of stages that occurs when the material is 

 handled in bulk by the student. 



For stages with embryonic shield and germ-ring the preceding 

 method should be used if the yolk is opaque ; but a better plan is to 

 secure the small transparent eggs of the runner (Gtenolabrus) and mount 

 them in formalin in a hollow ground slide, sealing the edges of the 

 cover-slip with cement. Staining is not required. In this egg either 

 the upper or under surface may be viewed simply by changing the focus. 



Preservation of Bryozoa.t — Bessie E>. Green gives the following 

 method which was successfully used for preserving CristateUa, PlumateUa, 



* Trans. Amer. Micr. Soc, xxxiii. (1914) pp. 54-5. 

 f Trans. Amer. Micr. Soc, xxxiii. (1914) pp. 55-6. 



